1. Field of the Invention
The present invention relates to a semiconductor chip including communication circuitry, and to methods of testing the semiconductor chip.
2. Description of the Related Art
Wireless communication devices must put out radio-frequency (RF) signals at a level high enough to assure an adequate transmission distance, but not so high as to interfere with other wireless communications or violate radio regulations. Semiconductor integrated circuit chips that include wireless communication circuitry are therefore tested before shipment to make sure that their RF signal levels are within designated ranges. Test equipment for carrying out these tests (such as the equipment shown in FIG. 16 in Japanese Patent Application Publication No. 2008-228038, for example) typically includes a pair of test devices that are externally connected to the chip under test. The chip receives an RF test signal from one test device and outputs a corresponding RF signal to the other test device, which measures the level of the RF output signal. If the measured signal level falls within the designated range, the chip passes the test.
A problem with this conventional test scheme is when RF signals are transferred between the test devices and the chip under test they are affected by the impedances of the chip-to-device interconnections, causing a loss of signal power. This loss makes precise signal level measurement difficult and lowers the reliability of the test result.
Another problem is that accurate measurement of an RF signal level requires an expensive analyzer.